This invention relates to an improved ice making machine having an evaporator with water pipes extending vertically therethrough and open through the top and bottom thereof. The evaporator is divided into a relatively large freezing chamber and a relatively small hot gas inlet chamber below the freezing chamber. Low pressure liquid refrigerant is fed into the evaporator at the bottom of the freezing chamber and gas refrigerant is drawn off at the top of the freezing chamber to freeze water flowing through the water tubes. When the tubes are almost filled with ice, hot gas is introduced from the hot gas inlet chamber to the bottom of the freezing chamber to warm the water tubes and release the ice so it will slide out for harvesting.
It is known in the prior art to include a short separate chamber at the bottom of the freezing chamber through which warm liquid refrigerant flows before continuing through the refrigeration circuit to the expansion valve. The warm liquid refrigerant passing through this chamber prevents excess ice build up at the lower ends of the water tubes, and thus, avoids difficulty in obtaining release of the ice when the hot gas is introduced through the side of the evaporator near the bottom of the freezing chamber. This small chamber also acts to cool the warm liquid refrigerant before it enters the expansion valve during the freezing period.